The ventricular system of the brain of human beings may be divided into the lateral ventricles, Monro's foramen, the third ventricle, aquaeduct, the fourth ventricle, foramen of Luschka, foramen of Magendie, etc. The subarachnoid spaces are located at the exterior of the brain and the spinal cord. The enlarged subarachnoid spaces located at the base of the brain are referred to as cisterns. The cerebrospinal fluid (hereinafter, CSF) is produced in the ventricular system and the subarachnoid spaces, and circulates within the ventricular system, the cisterns, the subarachnoid spaces, and finally to the arachnoid villi of the dural venous sinuses (sagittal sinus). The CSF is then absorbed through the venous sinuses into the blood circulation. If it is obstructed, the CSF will gradually increase and cause expansion of the ventricular system, the elevation of intracranial pressure, and the clinical symptoms of acute or chronic elevation of increased intracranial pressure. This condition referred to as hydrocephalus in medical science.
From the above description, it can be seen that hydrocephalus originates from obstruction to the circulation of CSF. It is generally treated by cutting off the obstruction focus, or bypassing the obstructed part by means of a shunting device, which is referred to as a hydrocephalus shunting procedure. Shunting procedures may be divided into extracranial shunting procedures and intracranial shunting procedures.
The theory of extracranial shunting procedures is to shunt the CSF to extracranial tissues or organs, where it can be absorbed by them. Of course, such a procedure is not consistent with normal CSF circulation and absorption physiology.
In extracranial shunting procedures, an extracranial shunting tube comprised of the intracranial and extracranial parts is used. The surgical operation may include : ventriculo-atrial shunt, ventriculo-peritoneal shunt, ventriculo-pleural shunt, limbo-peritoneal, shunt and other types of extracranial shunts which are rarely used. In current practive, the ventriculo-peritonial shunt is the type most commonly used for the treatment of various kinds of hydrocephalus. However clinical experience has proven that it is still not an ideal procedure. The major shortcoming lies in the fact that the extracranial tube consists of a ventricular tube, a reservoir and a distal tube. The valve in the reservoir or in the distal tube and the anti-siphon device, is often found unable to regulate and draw an appropriate quantity of CSF for proper circulation. Various complications relating to over drainage of CSF in the ventricies may result, such as chronic subdural hemorrhage, slit ventricle syndrome, isolated enlargement of the fourth ventricle, etc. In addition, defects may also be caused by a defective shunting tube. Such defects may include both obstruction at the end of the ventricular catheter, and breaking and/or falling off of the joining parts which link the vertricular tube, the reservoir, and the distal tube. In the ventriculo-peritoneal shunt which is most commonly used, there are also possibilities of various peritoneal complications, such as inguinal hernial, hydrocele, false pocket inside the peritoneum (pseudocyst) and peritonitis caused by shunt infection, perforation of the intestine or perforation of the peritoneal wall by a shunting tube, twisting of intestine (volvulus), etc. Infection after a shunting procedure (shunt infection) is a serious complication. The infection after ventriculo-peritoneal shunt operation usuallu causes venticulistis and peritonitis (inflammation of the ventricular system of the brain and the peritoneal cavity). In view of these defects, it is apparent that the ventriculo-peritoneal shunting procedures which are commonly used at the present time are still not adequate.
In addition to the aforementioned extracranial shunting procedures, intracranial shunting procedures are also available. The basic theory of these intracranial shunting procedures is the use of a surgical operation or a shunting tube to enable the CUS to bypass the obstruction and circulate to the subarachnoid space, so as to be absorbed by the arachnoid villi. This is consistent with the physiology of normal circulation of the CSF.
Intracranial shunting procedures include (1) ventriculo-sagittal sinus shunt, (2) ventriculo subarachnoid space shunt, (3) ventriculo-cisternal shunt, (4) the third ventriculostomy, and (5) the third-fourth ventricular shunt. Senn in 1908 and Forrest in 1957 both reported the results of treating hydrocephalus by using a perforated rubber tube in their ventriculo-subdural shunting procedures. The theory of these shunting procedures is to circulate the CSF through the shunting tube to the subarachnoid space on the surface of the cerebrum to be further absorbed by the arachnoid villi for blood circulation. However, no further report has been made since 1957. Presently, the above mentioned shunting procedures numbers (3), (4) and (5) are still occasionally used by some neurosurgeons, but they are not always applicable for the treatment of all forms of hydrocephalus.
In view of the defects described in the preceding sections prior art and techniques concerning the treatment of hydrocephalus by the application of extracranial shunts and the intracranial shunts, the inventors have devoted themselves, with their years of accumulated experimental and clinical experience, to the development of the present invention which will provide better treatment of hydrocephalus and ultimately be of great benefit to patients.
The main novelty of the present invention is that it provides certain features which should be found in an ideal shunting tube that will shunt only the excessive CSF an then still maintain a normal intracranial pressure, and cause fewer consequent complications by avoiding those problems associated with the reservoir, connector, and distal end.
Such a feature of the present invention is its adoption of an intracranial ventriculo-subdural shunt which is compatible with the physiology of the circulation of CSF.
Still another feature of the present invention is found in its shunting tube which is composed of a thin film and a ventricular tube, made of hydrogel such as hydrophilic polymer material which has proved to be of obvious benefit in medical treatment of this condition.